Collins told TV Line: "He comes back with amnesia, which is probably a good thing for him because he isn't too happy with what he's done. So the fact that he doesn't remember it is probably nice for him.

"He doesn't have to suffer quite as much when he first comes back. But there will be plenty of suffering for Cas to come."

Collins added that the character is a "version of Cas that we have, to a certain extent, seen before".

"A lot of people are just going to be excited to see Cas again," he continued. "And of course, as things twist and turn, there's going to be a lot of people who are really disappointed that it's not exactly how they want it."

Collins also described his return to the set of Supernatural as "like a family reunion", stating: "It was like nobody had changed and everything was the same. We really picked up right where we left off. It was actually a little bit spooky the extent to which it felt like I had never left.

"It's just a really, really great group of people to work with, and it's a fun place to come to work."